It is well known that it is necessary in a receiver of a cellular mobile radio system to recover each communicated signal under varying and challenging conditions. These conditions include, for example, the presence of multi-path signals and fading resulting in low signal-to-noise ratio (SNR), the presence of strong co-channel interfering (CCI) signals, and Doppler effects due to relative movement of the signal transmitter and receiver, as well as typical constraints due to factors such as limited channel bandwidth and equipment tolerances. In the case of a TDMA system, it is necessary to recover the timing and synchronize to the time division multiplex (TDM) frames and time slots of a received digital communications signal. It is also desirable to provide the receiver with the least possible cost and computational complexity.
International Publication Number WO 97/08867 dated division multiple access) systems. Mar. 6, 1997, in the name of Northern Telecom Limited and entitled “Timing Recovery And Frame Synchronization In A Cellular Communications System”, discloses a method of timing recovery in which indirect variables of a linear complex vector are estimated using a maximum likelihood criterion in order to recover sampling delay and hence the timing and frame synchronization of the received signal.
There remains a need to provide improved receivers for cellular communications systems.